1. Field of the Invention
This invention relates to an automatic polarization analyser for measuring a variation in the polarized condition of light when the light has passed through a sample and automatically measuring the phase difference .DELTA. and the amplitude-reflection ratio angle (azimuth angle) .PSI. of the sample to automatically indicate their respective values.
2. Description of the Prior Art
The automatic polarization analyser device to which the present invention relates may be of two types, namely, the reflection type and the transmission type. Where the automatic polarization analyser device is of the reflection type, it has a polarizing optical system comprising a light source, a polarizer mounted for rotation about the optical axis of the system, a 1/4 wavelength plate having its azimuth angle set to -45.degree. or +45.degree. with respect to a reference azimuth (the surface of incidence of a sample), a 1/2 wavelength plate mounted for rotation about the optical axis, light modulator means for phase difference modulation and azimuth angle modulation, an analyser having its azimuth angle set to 0.degree. (if the azimuth angle of the 1/4 wavelength plate is -45.degree.) or 90.degree. (if the azimuth angle of the 1/4 wavelength plate is +45.degree.) with respect to the reference azimuth, and a photoelectric converter. Where the automatic polarization analyser device is of the transmission type, it has a polarizing optical system comprising a light source, a polarizer mounted for rotation about the optical axis of the system, a 1/4 wavelength plate having its azimuth angle set to -45.degree. or +45.degree. with respect to a reference azimuth (the axial azimuth of the analyser), a sample having its axial azimuth set to said reference azimuth, a 1/2 wavelength plate mounted for rotation about the optical axis, light modulator means for phase difference modulation and azimuth angle modulation, an analyser, and a photoelectric converter. In any of these devices, the polarizer and the 1/2 wavelength plate are automatically controlled to individually obtain a value which determines the phase difference .DELTA. of the sample from the angle of rotation of the polarizer and a value which determines the amplitude-reflection ratio angle .PSI. of the sample from the angle of rotation of the 1/20 wavelength plate, whereby the phase difference .DELTA. and the amplitude-reflection ratio angle .PSI. are indicated.
Although these conventional devices can achieve the automatic control and the automatic indication if the phase difference .DELTA. is within the range of 0.degree..ltoreq..DELTA. .ltoreq.1/2.degree., they are disadvantageous in that such automatic control and indication may not be achieved if the phase difference .DELTA. is within the range of 180.degree..ltoreq..DELTA..ltoreq.360.degree..